Use of video display terminals (VDT) in data processing equipment, office automation equipment, video games and TV is increasing rapidly. But as know, the glare and reflected light generated from the surface of a cathode ray tube (CRT) can cause eye fatigue, added eye pressure, headache, etc. Emission of low frequency radiation and electrostatic charges from a VDT can be even more harmful. At the 1986 and 1989 International Scientific Conference, aimed at Work With Display Units (WWDU), a number of such cases were reported by scientists and doctors. In their reports, it was noted that electrostatic charges can attract bacteria or pollutants with an opposite charge to the screen. Thereafter, other bacteria or pollutants having the same charge can bombard the operator when replaced by the bacteria on the screen.
In addition, a controversy over non-ionization radiation has continued on for years. Though electromagnetic radiation generated from screen is well below an injury-causing level, such low frequency radiation does exist. Some old-fashioned or inferior VDTs emit radiation over the limit permitted by government regulations and guidelines. A prior art anti-static CRT has been developed to overcome this problem. The prior art method of coating the CRT surface with a thin, transparent conductive layer leaves a high electric resistance impending conduction. Moreover, the thin transparent layer, results in reflection and diffusion of light.
VDTs are available with many different characteristics. For instance, they can vary in viewing diagonal from 5" to 40"; in screen surface they can vary from cylinderical, spherical to flat surfaces; in color from mono-chrome, 2-color, 4-color, 16-color, even to 160-million color; in resolution from 160X200, 320X200, 640X200, 640X480, to 4096X4096. In fact, in any type of CRT whether monochromatic or color, a few naturally defective points like missing phospher dots (M.P.D.), blemishes and small scratches are admitted. In color CRT especially, a heat-causing expansion of aperture of the shadow mask thereof, which is generally iron material or iron-nickel alloy, may sometimes lead to the phenomenon of distorted images, Moires and/or Newton Rings. In prior art U.S. Pat. Nos. 4,253,737; 4,468,702; 4,760,456; 4,788,597; 4,974,935, solution of such problems are not presented.
The device of patent '737 is directed to overcoming glare and reflected light. However, because pollutants can easily be attracted to and stick to the mesh, the viewing is obstructed and Moires and/or Newton Rings occur. The device of patent '702 uses nylon yarns with a conductive thread-woven central area. This weaving is very complicated, but does not produce any better result than the present invention. The device of patent '597 includes a conductive mesh, a moveable frame in size adapted to CRT front frame (bezel) and a ground wire. The bezel construction result is very complicated resulting in a significant increase in cost.
The device of patent '935 includes a conductive mesh, a rigid frame and a ground wire, and is characterized by a fiber diameter between 20-100 .mu.m, an aperture between 45-230 .mu.m and formed angle with frame between 10.degree.-45.degree.. In experiments it was found to be unable to fit any kind of VDT.